Earth and Climatic Studies

Ocean Colour

Ocean-colour variables are chlorophyll-a concentration,vertical diffuse attenuation of the light, (Kd) and total suspended matter (TSM)concentration in coastal waters. Ocean Color Monitor (OCM-2) sensor of Oceansat -2 satellite is designed to obtain quantitative information on these parameters. Ocean-colour information derived from OCM data will alsobe useful for studying the aerosol transport and terrestrial bio-sphere. Calibration and validation of ocean color products for coastal waters is being studies.

Ocean colour sensors provides valuable information for understanding some of the key scientific issues like spatial and temporal distribution of phytoplankton blooms with the magnitude and variability of primary production on global scale, computation of regional and basin scale marine primary production, quantification of oceans role in global carbon cycle and other bio-geochemical cycles, Identification and quantification of relationship between ocean physics and large scale patterns of productivity, elucidate the complex mechanism between upwelling and large scale circulation patterns in ocean basins, better understanding of the processes associated with mixing along the edge of coastal currents, eddies, western boundary currents and fronts.

Information on ocean colour is critical for identification of Potential Fishing Zones (PFZ) for improving catch efficiency, accurate and detailed understanding of the oceanographic environment for offshore platform design for reducing the risks, timely information on strong currents, eddies, fronts, sediment plumes and mixing zones, for ocean environmental monitoring. Synoptic maps of ocean colour (chlorophyll) spatial structure of pelagic ecosystem at synoptic scales can be generated from Ocean colour information.

Ocean Chlorophyll

Multi-source and multi-temporal data from earliest possible topographical maps and satellite remote sensing datasets were used to map the forest cover in the country over last eight decades (1930, 1975, 1985, 1995, 2005 and 2013/2014). Forest fraction cover information was hosted on Bhuvan-Forest Fraction Cover.

Studies are carried out on overall annual net rate of deforestation over long term, deforestation rate at regional level. It contributes for the evaluation of biodiversity. Fractional forest cover maps and forest type maps of Indiawere hosted on Bhuvan website for decision makers, extension agencies and researchers for understanding regional level forest cover changes and studies related to vegetation-climate modeling.

Vertical diffuse attenuation of the light (Kd)

The diffuse attenuation coefficient for down welling irradiance Kd (in inverse meters), is one of the most commonly determined (quasi) optical properties (a descriptor of the underwater light field that varies with depth) of seawater. Kd is an indicator of the penetrative component of solar radiation. Approximately 90% of the diffuse reflected light from a water body comes from a surface layer of water of depth 1/Kd. Thus, Kd is an important parameter for remote sensing of ocean colour.

IOCM-2 Chlorophyll (OC2 & OC4) algorithms and Diffuse attenuation coefficient at 490 nm products has been generated using SeaDAS (SeaWiFS Data Analysis System) for Local (North Indian Ocean/LAC) and for Global Oceans(GAC). For NIO,2-day,8-day,monthly at 1KM and above, Globe 8-day and Monthly 4KM and above products are generated from 2010.

8 day, Monthly products are generated since 2011 and hosted on Bhuvan-Diffuse Attenuation Coefficient.

Select NICES Project - Terrestrial Sciences –Chlorophyll products and List and view the data of the selected time period. Technical Document(hyper link : OCM-2-SeaDAS-TR-2.pdf)

Total Alkalinity and Dissolved Inorganic carbon

Total alkalinity as the name suggest reflects the ability of seawater to resist acidification in oceanographic perspective. In almost all natural waters alkalinity is produced by dissolved carbon dioxide species, bicarbonates and carbonates. Knowing the total alkalinity and the buffering capacity of any one area of the ocean helps us to correlate changes that we see in biologyto what is happening with the chemistry in the atmosphere and the ocean and form an essential carbon parameter. Dissolved inorganic carbon DIC of the seawater sample is the sum of the concentrations of the dissolved inorganic carbon species. Since alkalinity (TA) and DIC are conservative therefore both are used in ocean carbon models. Both DIC and TA can be used to estimate the air-sea CO2 fluxes in combination with satellite based approach can help us to map the large scale spatio temporal distribution in the ocean and further discussed below.

Combined satellite data (Sea Level Anomalies, Mean Dynamic Topography and Sea Surface Temperature) and in-situ (Temperature and Salinity profiles) on a 1/4 degree regular grid (from http://marine.copernicus.eu/), satellite chlorophyll MODIS AQUA 4 KM resolution data (from https://podaac.jpl.nasa.gov/dataset/MODIS_Aqua_L3_CHLA_Daily_4km_) for computing the DIC values are used. These products are now being available as a part of NICES programme at 1/4 degree resolution globally. Monthly products are generated for 2014-2017 and hosted on Bhuvan-Dissolved Inorganic Carbon.

Select NICES Project - Terrestrial Sciences –Dissolved Organic Carbon and List and view the data of the selected time period.

Daily Tropical Cyclone Heat Potential

Tropical cyclone heat potential (TCHP), is estimated using (a) sea surface height anomaly (SSHA) from the available altimeters, (b) sea surface temperature (SST) from Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI), and (c) the climatological values of the depth of the 26°C isotherm (D26) using Artificial Neural Networks approach. It is generated on a daily basis from 1998 to present with a one week time delay.

Daily Tropical cyclone heat potential (TCHP)information is generated since 1998 and hosted on Bhuvan-TCHP.

Select NICES Project - Terrestrial Sciences –Tropical cyclone heat potential and List and view the data of the selected time period. Technical Document(hyper link :TCHP_OHC&OMT)

Ocean Heat Content

Ocean Heat Content up to 700m depth (OHC700) is an important ocean climatic parameter required for atmospheric and oceanographic studies. This is obtained by summing the heat content of the ocean column from the sea surface to a depth of 700m.

Ocean Heat Content (OHC) and Ocean Mean Temperature (OMT) are important climatic parameters required for atmospheric and oceanic studies like cyclone and monsoon predictions and ocean heat transport estimations. Ocean Heat Content information is generated since 2001 and hosted on Bhuvan-OHC.

Select NICES Project - Terrestrial Sciences –Tropical cyclone heat content and List and view the data of the selected time period. Technical Document(hyper link :TCHP_OHC&OMT.

Ocean Mean temperatures and Heat Content information is generated since 2001 and hosted on Bhuvan-OMT-OHC.

Select NICES Project - Terrestrial Sciences –Ocean Mean temperatures and Heat Content and List and view the data of the selected time period. Technical Document(hyper link :TCHP_OHC&OMT)

Co Tidal Map

Total alkalinity as the name suggest reflects the ability of seawater to resist acidification in oceanographic perspective. In almost all natural waters alkalinity is produced by dissolved carbon dioxide species, bicarbonates and carbonates. Knowing the total alkalinity and the buffering capacity of any one area of the ocean helps us to correlate changes that we see in biologyto what is happening with the chemistry in the atmosphere and the ocean and form an essential carbon parameter. Dissolved inorganic carbon DIC of the seawater sample is the sum of the concentrations of the dissolved inorganic carbon species. Since alkalinity (TA) and DIC are conservative therefore both are used in ocean carbon models. Both DIC and TA can be used to estimate the air-sea CO2 fluxes in combination with satellite based approach can help us to map the large scale spatio temporal distribution in the ocean and further discussed below.

Combined satellite data (Sea Level Anomalies, Mean Dynamic Topography and Sea Surface Temperature) and in-situ (Temperature and Salinity profiles) on a 1/4 degree regular grid (from http://marine.copernicus.eu/), satellite chlorophyll MODIS AQUA 4 KM resolution data (from https://podaac.jpl.nasa.gov/dataset/MODIS_Aqua_L3_CHLA_Daily_4km_) for computing the DIC values are used. These products are now being available as a part of NICES programme at 1/4 degree resolution globally. Monthly products are generated for 2014-2017 and hosted on Bhuvan-Dissolved Inorganic Carbon.

Select NICES Project - Terrestrial Sciences –Dissolved Organic Carbon and List and view the data of the selected time period.

Eddy Kinetic Energy

Eddy Kinetic Energy represents dynamic fields indicate boundaries of mass convergence and divergence areas of the ocean environment. Associated with Mean Sea level Anomaly (MSLA) maps convey the areas of ocean water sinking and upwelling, which help in many ways to understand the processes of primary productivity, air-sea gas flux and mass drift in the surface layers. Data is generated since Jan-1993 to Dec-2011.

Eddy Kinetic Energy information is hosted on Bhuvan-Eddy Kinetic Energy.

Select NICES Project - Terrestrial Sciences –Eddy Kinetic Energy,List and view the data of the selected time period .Technical Document(hyper link :EKE_NEW)

Ekman and Geostrophic Currents

The ocean surface currents are estimated from satellite observations of surface wind from Oceansat-2 Scatterometer and Sea Surface height from SARAL AltiKa. The Ekman Surface current estimated from wind stress components and geostrophic current estimated form SARAL AltiKa are combined to generated ocean surface currents. The data sets available since March 2013. The products are validated with drifting buoy observations indicating a good relationship between the observations.

The wind-driven currents (or Ekman currents) are the resultant of frictional force exerted by wind on the ocean surface. The wind blows across the ocean and moves its waters as a result of its frictional drag on the surface. Once the wind sets surface waters in motion as a current, the Coriolis force, Ekman transport, and the configuration of the ocean basin (topography) modify the speed and direction of the current.Ekman Currents are estimated using data from scatterometer sensors, viz., OSCAT (April, 2013 - Feb,2017) and SCATSAT (Mar,2017-till date) wind composites on a daily basis.

Under the effect of the pressure-gradient force, the water tends to move from the region of high pressure to that of low pressure. And this flow of water balanced by Coriolis force leads to Geostrophic currents. Geostrophic currents are proportional to the height gradient divided by the Earth's rotation parameter f, which is the lowest-order balance for quasi-steady circulation at higher latitudes. Height gradient has been computed by using Saral-AltiKa sea surface height anomaly (SSHA) and mean dynamic topography data. Geostrophic Currents are computed on daily basis by assimilating and gridding the past 15 days along track SSHA data.

Ekman Currents information is hosted on Bhuvan-Ekman Curretns, Select NICES Project - Terrestrial Sciences –Ekman Currents , List and view the data of the selected time period. Technical Document(hyper link : Ekman Currents)

Geostrophic currents information is hosted on Bhuvan-Geostrophic currents . Select NICES Project - Terrestrial Sciences –Geostrophic Currents, List and view the data of the selected time period. Technical Document(hyper link : Geostrophic Currents)

Mean Sea Level Anomaly

Eddy Kinetic Energy represents dynamic fields indicate boundaries of mass convergence and divergence areas of the ocean environment. Associated with MSLA the maps convey the areas of ocean water sinking and upwelling, which help in may ways to understand the processes of primary productivity, air-sea gas flux and mass drift in the surface layers.

Monthly data is available on mean sea level anomaly from 1991-2011 and is hosted on Bhuvan-MSLA. Select NICES Project - Terrestrial Sciences –Mean Seal Level Anomaly, List and view the data of the selected time period. Technical Document(hyper link : Mean Seal Level Anomaly)

Model Derived Depth Isotherm

The Depth of the 26° isotherm in the ocean is represented as D26. It is obtained by scanning the ocean temperature profile from the surface to the depth where temperature reaches 26° C. It gives an idea of the depth to which the warm surface layer of the ocean extends. This parameter is particularly of interest to oceanographers and atmospheric scientists studying the genesis, intensification and propagation of cyclones as well as their impacts.

Daily Model Derived Depth Isotherm information from 2013-2018is hosted on Bhuvan-Isotherm .

Select NICES Project - Terrestrial Sciences –Daily Model Derived Depth Isotherm, List and view the data of the selected time period. Technical Document(hyper link :Isotherm26o)

Ocean Wind Curl

Wind Stress Curl is the measure of the rotation of the wind stress (or ocean surface circulation). The curl of wind stress is helpful in identifying areas of cyclogenesis and their propagation. OSCAT 2-days Wind Stress Curl Composites have been generated by computing the curl of wind stress field, which is estimated using DIVA generated wind field composites. These products are available on daily basis from 2010 to 2013. Further details have been provided in the technical document.

Daily OSCAT Ocean wind curl at 25Km, 50Km grid data from 2010-2014, daily SCATSAT Ocean wind curl at 25Km, 50Km grid data from 2016-18 are hosted on Bhuvan-Ocean Wind Curl.

Select NICES Project - Terrestrial Sciences –Ocean wind curl, List and view the data of the selected time period. Technical Documents :(hyper link :OSCAT Ocean wind curl 50Km, OSCAT Ocean wind curl 25Km)

Ocean Wind Stress

Wind stress is defined as the tangential (drag) force per unit area exerted on the surface of the ocean by the adjacent layer of moving air. Wind stress is the most important forcing parameter in the upper ocean circulation. OSCAT Daily Wind Stress Composites have been generated using DIVA generated 2-days wind field composites. For wind stress computation, Large and Pond (1981) drag coefficients, modified by Trenberth et al. 1990, are used. These products are available on daily basis from 2010-2013. The output products consist of zonal and meridional wind stress components.

Daily OSCAT Ocean wind stress at 25Km, 50Km grid data from 2010-2014, daily SCATSAT Ocean wind curl at 25Km, 50Km grid data from 2016-18 are hosted on Bhuvan-Ocean Wind Curl.

Select NICES Project - Terrestrial Sciences - Ocean wind stress, List and view the data of the selected time period. Technical Documents:(hyper link :OSCAT Ocean wind stress 50Km, OSCAT Ocean wind stress 25Km)

Sea Level Pressure

The pressure charts prepared by interpolatingpoint measurements/generated through Numerical Weather Forecast (NWF) models or data assimilation techniques. But these data sets may not provide true field situation. As of today, no remote sensing sensor is capable to measure the pressure fields directly. In the present technical report we presented the methodology of retrieve pressure fields from Quick-Scat/Oceansat-2 Scatterometer (OSCAT) winds using the University of Washington Planetary Boundary Layer (UWPBL) model of Patoux et al (2003) during some selected period. These pressure values are validated with all the available in situ observations.

Daily Sea level pressure data from 2010-2014 is hosted on Bhuvan-Seal level pressure.

Select NICES Project - Terrestrial Sciences –Seal level pressure , List and view the data of the selected time period. Technical Document(hyper link :SCATSAT sea level pressure)

Ocean Surface Currents

The ocean surface current from the satellite is estimated by combining geostrophic current from Saral-AltiKa and Ekman current from OSCAT. Total currents have their utility in the studies of ocean dynamics, coastal circulation and upwelling and sinking processes at the sea. Application of the product will also be explored with the studies of dispersion analysis of marine pollutants like algal blooms, coastal sediments, oil spills and debris. These products are available on daily basis for the period of availability of data from both the satellites.

Daily Ocean surface currents data from 2013--2018 is hosted on Bhuvan-Ocean Surface Currents.

Select NICES Project - Terrestrial Sciences –Ocean surface Currents, List and view the data of the selected time period. Technical Document(hyper link :Ocean surface currents)

Sea Surface Height

Sea Surface Height (SSH) map has been generated by gridding Saral-AltiKa along track data. For gridding, median interpolation of last 15 days along track data has been done.

Daily Sea surface height data from 2013--2018 is hosted on Bhuvan-Sea Surface height . Select NICES Project - Terrestrial Sciences –Sea surface height , List and view the data of the selected time period. Technical Document(hyper link :Sea surface height)

Ocean Winds

Surface winds over oceans are required for several operational, oceanographic, atmospheric and climatological studies. OSCAT 2-days Wind Composites have been generated by interpolating OSCAT level-3 wind fields data using Variational Inverse Method (VIM) inbuilt in Data-Interpolating Variational Analysis (DIVA) software. These products have their utility in daily weather and modeling activities. The output products consist of zonal and meridional wind components with their respective error fields as computed by DIVA.

Daily OSCAT Ocean winds at 25Km, 50Km grid data from 2010-2014, daily SCATSAT Ocean winds at 25Km, 50Km grid data from 2016-18 are hosted on Bhuvan-Ocean Winds.

Select NICES Project - Terrestrial Sciences –Ocean winds, List and view the data of the selected time period. Technical Document (hyper link :OSCAT Ocean winds 50Km, OSCAT Ocean winds 25Km)